Kangaroos forward coach Brett Allison believed it was a vital piece in the jigsaw puzzle that saw the club overcome a bad start to qualify for its first final since 2008.

"Playing three big forwards was something we had in mind from the start of last season, but unfortunately Lachie Hansen was injured and suspended in the reserves," Allison said.

"It took us a long time to see it in action. But when we tried it, it seemed to work and we think it was a key factor in helping us turn our season around."

North Melbourne was sitting 12th when Petrie, Tarrant and Hansen all played in attack against Adelaide in Round 13, for the first time last year.

It was the start of nine wins from the last 12 games, lifting the Roos into the finals before an elimination final wipe-out against West Coast.

One of those was against the Magpies in Round 21, when Petrie and Tarrant kicked three goals and Hansen two in the five-goal win.

"It has been a pretty good weapon," Petrie said of the three-pronged tall attack. "We managed to make opposition defences play three talls and when they haven't, we have been able to get on top of them."

The three Roos forwards kicked an accurate total of 102 goals and 38 behinds last year - Petrie 58.18, Tarrant 23.16 and Hansen 20.4.

In their 12 games as a trio last year, they booted a total of 76.21.

"Lachie is laid-back and relaxed and is a real character," Allison said. "Robbie is far more serious about his footy and is very focused.

"Drewie is probably in between the two of them.

"They are all different and maybe that's why it worked so well."

Petrie, 30, has been a star for the Kangaroos since his 2001 debut, but his 2010 season was ruined by a foot injury.

His past two seasons have yielded 106 goals and he has been in near career-best form.

"He takes a lot of pressure off Lachie and I," Tarrant said. "As much as we want the ball, you don't mind it when the mids kick it long to the big fellow.

"He is an awesome leader down there and is a very selfless player."

Tarrant, almost 24, endured four shoulder reconstructions early in his career. His 16 games last season was the sort of return that most North fans hoped for.

"Taz works his backside off," Hansen said. Added Petrie: "Taz had so many shoulder problems and he played as a defender for a while just to get some game time. But he showed last year that he has really grown as a player."

Hansen, 24, and a one-time No.3 draft pick, spent time alternating between attack and defence, but seems to have found his right home.

"Lachie is a strong mark and is athletic, which means he is a tough player to match up on," Petrie said.

The three forwards hope to stretch some more opposition defences this year, starting with Collingwood today.

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